Printing techniques can be classified into direct or indirect methods. In the former, the ink is directly deposited upon a printing substrate to form the desired ink image. In indirect processes, the ink is deposited on an intermediate member and subsequently transferred to the substrate, this intermediate member being therefore also termed an intermediate transfer member or simply a transfer member. Typically, the ink deposited thereon is modified or treated (e.g., dried, cured, fused, etc.) before being transferred as a so-called ink image to the substrate. Indirect printing can be analogue, the transfer member providing a particular ink image while being used in a print job (offset printing is one example of this type), or digital. Digital printing techniques have been developed that allow a printer to receive instructions directly from a computer, without the need to prepare printing plates.
A variety of digital printing processes exist, each differing in the kind of inks that may be used, the type of modification (if any) the ink deposited on the transfer member undergoes and the manner such transfer can be effected. For example, dry toners are used in the xerographic process, electrically chargeable inks are used in electrophotography, and so on. The inks, which generally include a coloring agent (e.g., a dye or a pigment) in a polymeric system, can be in dry form, paste form or liquid form, the liquid carrier, if any, being either aqueous or organic. The transfer members for such printing systems may be required to fulfil different characteristics, depending on the exact process in which they are to serve. Nevertheless, they may share common properties and structural principles. The present disclosure is concerned with the construction of a transfer member that may be employed inter alia in printing processes as detailed in WO2013/132418, WO2013/132420, WO2016/189512 and WO2018/100528, but may also find application in other indirect printing systems.
The transfer member described in the afore-mentioned applications may be a drum or a continuous loop belt which comprises a flexible blanket having an imaging layer, with a hydrophobic outer surface also referred to as a release layer, and a support layer. The present disclosure is particularly concerned with the preparation of the imaging layer, but should not be construed as being limited thereto.